Propeller pump



Aug. 17 1926. 1,596,459

H. F. SCHMIDT PROPELLER PUMP Original Filed June 9. 1924 4 Sheets-Sheet1 h'. fchmidt Wl NES S INVENTOR yg l BY $7 09W ATTORNEY Aug; 17 192e.1,596,459

H. F. SCHMIDT PROPELLER PUMP A original Filed June 9. 1924 4 sheetssheet2 H. /'Sahmidf WITNEssEs; lNvENToR l' BY ATTORNEY Aug. 17 1926.

H. F. SCHMIDT PROPELLER PUMP Original Filed June 9. 1924 2Q 4o in BU non4 Sheets-Sheet 3 RATID or Ptonscvsv T0 msc AIEAL' l Z El 4 5 RATIO 0FFITCH RATIOS ga l0.

NUMBER oF BLAvEa on PRoPElLcn 6FT ll.

H. f.' .Schmidt l INVENTOR ATTORNEY Aug. 17 1926. 1,596,459

H. F. SCHMIDT PHOPELLER PUMP o-iginnl Filed June 9` 1924 4 shuts-sheet 4fl. ESC/70712!! WITNESSES: INVENTOR l' BY ATTORNEY Patented Aug. 17,1926.

HENRY F. SCHMIDT, 0F LANSDO ELECTRIC & MANUFACTURING C0.,

WNE, PENNSYLVANIA, ASSIGNOR T0 WESTINGHOUSE A CORPORATION OFPENNSYLVANIA.

IPROPELLER PUMP.

Application llled. June 9, 1924, Serial No. 718.906. Renewed .Tune 25,1926.

This application of my application, April 6, 1920, and i Serial No.573,050,

is a continuation in art Serial N o. 371,648, led n part of myapplication, filed July 5, 1922.

This invention relates to propeller pumps and it lias of this type whichfor an object to produce a pump is simple in construction and is moreefficient than similar pumps noW in use-and known to me.

A further object pump in which the spacing of the disk area of the theblades, ratios of the blades, portions of the fluid is to produce apropeller propeller, the axial pitch and the areas and propassages ofthe pump casings are so proportioned and co-related as to produce a pumpin which losses, due to shock and cavitation nated.

These and other de more apparent throughout the further aresubstantially elimiobjects, which will be description of the invention,are attained by means of`a pump embodying the features herein describedand illustrated.

In the drawings accompanying and forming a part hereof Fig. 1 is asomewhat diagrammatic longitudidnal sectional view of a propeller pumpembodying my invention. Fig. 2 is a side elevation of a propellerembodying features of my invention and forming a detail of the Fig. 1.Fig. 2Ll is propeller shown in elusive, are diagrammatic views apparatusillustrated in an end elevation of the Fig. 2. Figs. 3 to 8ingraphicallyillustrating principles employed in pumps cally setting forth invention.

Figs. 9, 10 and 11 ves or diagrams graphifeatures of pumps em.- Figs. 12to 15, in-

clusive, are diagrammatic views explanatory of principles involved in myinvention. Fig.

1G 1s a diagrammatic view showing the effect of the vena contractapropeller design.

(zo-efficient upon the Throughout the further description of myinvention I have employed the in its broad sense, gases and liquids,

word fluid that is, to include both and the term pump is employed in itsbroad sense, since I do not desire to limit my invention to pump for usein connection with non-compressible fluids.

leferiing to the In Figs. 1 and 2 drawings I show more or lessdiagrammatically a practical arrangement of a propeller pump embodyingmy invention. The pump includes a casing 15 provided Witli an inlet port16 and a delivery port 17. As is usual in pumps of this character, thefluid delivery passages converge from the inlet port 16 to a throat atwhich the propeller is located. This convergence is for the purpose ofreducing the velocity of flow at the inlet and incidentally occasions anincrease in velocity of How at the throat such that, under normaloperating conditions,the fluid is moving at substantially the axialdischarge velocity when acted upon by the propeller. The casing is alsoshown provided with a divergent outlet which extends from the throat tothe port 17. This is also a usual construction and occasions a velocityconversion by which the kinetic or velocity energly of the fluid leavingthe propeller is trans ormed into potential energy in the form ofpressure.

The propeller 18 is shown mounted on a shaft 19 which extends through asuitable journal formed integrally with the casing 15 and provided atone end with a suitable packing 20. The ropeller illustrated is providedwith two b ades 21 and, as has been said, is located at the throatformed by the convergin -diverging fluid passages of the casing. T e hubportion 2la of the propeller is tapered from the inlet to the outletside of the propeller so as to occasion an additional contraction of thestream lines as the fluid passes through the propeller. In addition tothis the tapered hub is employed for the purpose of preventingaphenomenon analogous to that occasioned Vby obstructing the free flowto all sides of an orifice. This is ordinaril termed a suppressedorifice where the ow of one or more sides of the orifice is prevented bythe proximity of a Wall or diaphragm. In the drawings I have shown astationary cone or tail piece 22, which, in effect, forms a continuationof the hub portion and is held in place by the directing varies 23. Thetail piece is so proportioned that it forms one wall of the divergingannular passage between the propeller and the outlet port 17. Thedirecting varies 23 are so designed and so located that they re-directthe Huid issuing from the propeller and deliver it in a directionsubstantially parallel to the axis of the propeller. It will be apparentthat the vanes areemployed primarily for the purpose of converting therotary velocity of the fluid leaving the proller into effective velocityalong lines parallel to the axis of the propeller. These vanes are soproportioned and disposed that the inlet edges are substantiallytangential to the lines of flow leavin the propeller and the fluid isgradually de ected so that the change is accomplished with no shock anda minimum loss occasioned by surface friction.

For the purpose of maintaining substantially uniform flow throughout theinlet passages, I employ directing diaphragme 25 which sub-divide theinlet into at least two sections. These diaphragme are so formed anddisposed that they conform closely to the lines of fluid ilow, and bydividing the flow, occasion less variation in velocity past pointsdefined by any transverse plane, than would be the case if no diaphragmswere employed. The pro eller pump shown in the drawings comprises acasing of the el bow type, one leg of which constitutes the entrance legand the other lea` o'f which is provided with convergin and divergingportions and constitutes t e pumping leg.

The casing is provided with an inwardlyprojecting bearing 19' which isin axial alignment with the pumping leg referred to and which su ports adrive shaft 19 extending externa y of the casing, the propeller 21 beingsecured to one end of the drive shaft so that it is supported in anoverhung manner. The hub portion 21 of the propeller is arrangedadjacent to one end of the bearing 19 and its external surface, ineiect, constitutes a continuation of the external surface of saidbearing. fairing cone or tail piece 22 is arranged at the discharge sideof the propeller with its base adjacent to the hub portion 21 so thatits external surface in e'ect constitutes a continuation of the externalsurface of the hub portion 21. The fairing cone or tail piece 22 issupported by directing vanes 23 which serve to correct for the angulardischarge of fluid by the propeller, that is, these guide vanesgradually change the direction of flow of the stream from the propellerso,

that it assumes a direction of flow axially of the diverging ortion.

The prope er is so formed that the projected area of the blades ismaterially less than the annulus area thereof, thereby avoiding theundesirable effects of interfering stream lines in the fiuid andresulting eddies at the inlet side of the propeller. The term projectedarea as applied to the blades of the roieller indicates the projectedarea of the Ela the axis of rotation of the propeller. The term annulusor disk area is used herein to designate the area of the annulus definedes upona plane perpendicular to by the outer peripheral face of the hub21 and the outer tips of the rotating blades 21. The hub 21'* is shownas being tapered; and, in determining the annulus area, the largediameter must be considered as defining the inner circle of the annulus.If the hub should be cylindrical, then the diameter thereofwould definesuch inner circle. The radial itch of the blades Vis constant. As theaxial) pitch of each blade increases from the inlet or leading edge tothe outlet forA trailing edge, the plitch ratio of the trailin edge isgreater t an the pitch ratio of the leading edge. This increase of pitchserves to accelerate the fluid as it traverses the propeller tocompensate both for the increase in velocity due to the contraction ofthe stream as it approaches and traverses the propeller and to thedischarge of fluid by the propeller at an angle. By the term itch ratioas herein employed is meant t e ratioV of the pitch of a blade at anypoint to the diameter of the propeller. For example, assuming apropeller having a 12 inch diameter and a pitch of 9 inches at itsleading edge and a pitch of 18 inches at its trailing edge, then thepitch ratio of the 12 and of the trailing edge leading edge is The ratioof pitch ratios of the trailing edge to the leading edge is, in thisillustration, divided by .which is equal to 2.

In constructing pumps embodyin my invention, I take cognizance of the'act that all particles of a fluid ilow along lines of A leastresistance toward the point of least pressure in the body of the fluid.The convergence of the stream lines set up within a cates that the iuidapproaches the orifice from all possible directions and that theconvergence of the stream lines Within the body of the Huid continueseven after the jet is formed. I, therefore, recognize the fact that themovement of the blades of a propeller through the fiuid acted uponoccasions a low through the body of the fluid along stream lines whichconverge toward the source of thedisturbance, or, in other words, extendin a direction parallel to the axis of rotation of the blades'of thepro` peller. I also reco ize the fact that the rotary motion of t epropeller blades delects the direction of flow of the iuid, therebyoccasioning a flow in a substantially helical path, and that this causesa further contraction of the streams of fluid. I also bear in mind thatthe blades are acting upon a fixed column of fluid or, in other words, Irecognize the condition occasioned by the fact that the fluid acted uponis confined by the pump casing prior to, during, and after the fluid hasbeen subjected to the direct action to the propeller blades. All thesefacts are taken into account in the construction and design of pumpsembodying my invention, and I have so constructed the pump that aco-relation of the different principles employed in its design isobtained in such a Way as to occasion a minimum loss in the transfer of'energy from the propeller to the fluid acted upon, and in the conversionof the velocity energy of the fluid to potential or pressure energy.

Referring to the drawings:

Fig. 3 is a diagrammatic illustration of a sharp-edged orifice. The venacontracte of the jet of fiuid'issuing from the orifice as Well as thestream lines which produce this contraction of the jet are illustrated.It is well known that the vena contracta evidences the fact that streamlines are set up in the entire body of the confined fluid and that thesestream lines tend to converge toward the center of the orifice.

In Fig. 4, I have diagrammatically illustrated a thin, flat platesubmerged in a body of fluid. By considering the flow occasioned underconditions illustrated in Fig.`

3, it will be ap arent that a transverse movement of the p ate 8 in thedirection of the arrow Will occasion a condition, so far as stream linesare concerned, which is similar to the condition graphically illustratedin Fig. 3. A uick transverse movement of' the plate in t e direction ofthe arrow will tend to create a vacuum immediately back of the plate andwill occasion a flow of fluid Within the body in an attempt to fill orprevent the vacuum created by the movement of the plate. This flow isalong stream lines Within the body of fluid similar to stream linesformed by the issuance of fluid through the sharp-edged orifice and theconditions of flow Will be very similar, since in Fig. 3, the flow isoccasloned by a reduction in pressure occasioned by the orifice, and inFig. 4, the flow is occasioned by a reduction in pressure within thebody of the liquid occasioned by the transverse movement of the late. Itwill be apparent that the entire ody of fluid Will be more or lessaffected by the displacement occasioned by the movement of the plate andthat the fluid behind and immediate] adjacent to the plate will flow ata velibcity substantially equal to the velocity of the plate and thatthe stream lines set up Will converge toward" the plate, the tendency,of course, being for the liquid to move along lines of least resistancetoward the incipient vacuum occasioned by the movement of the plate.A It

will, of course, be apparent that cavitation may not actually takeplace, but the effect of the movement of the plate will be the sameWithin the body of fluid and will differ only in degree if cavitationdoes actually take place.

Fig. 4, therefore, illustrates that a transverse movement of the platethrough a body of' fluid will set up converging stream lines throughoutthe body and that the convergence of' these streamlines is toward theorigin of the disturbance, in this case, the plate, and that thevelocity of the flow in the converging stream lines will increase as thestreams converge and that a maximum velocity Will be reached at a pointimmediately adjacent to the moving plate.

`In Fig. 5, I have diagrammatically illustrated two plates 8 and 8submerged in a body of fluid and adapted to be simultaneously movedthrough the fluid in lines parallel to each other and in directionsindicated by the arrows. It will be apparent that the movement of eachplate Will occasion a disturbance or a local drop in pres- Vsure Withinthe body of fluid and will thereby set up lines of flow throughout thebody which will conflict with the lines of flow set up by the otherplate." While it would be impossible to so space the plates that theflow occasioned by the displacement of one plate would not interfere tosome extent with the flow occasioned by the displacement of the otherplate, it will be apparent that the spacing of the plates may be suchthat under certain conditions of displacement, the lines of flow, whileinterfering, will not interfere to such an er: ent as to occasion eddycurrents which Will appreciably reduce the efficiency of the plates intheir function of creating two well-defined and substantially parallelstreams Within the body of' the liquid. It will be apparent that thcplates may be so spaced that under certain conditions of displacementeach plate will starve the other. By this I mean each plate may be sospaced that it will prevent the flow of liquid to the point of lowpressure occasioned by the movement of the other plate. In Fig. 5, Ihave graphically illustrated the direction of the lines of flowoccasioned by the movement of the two plates 8 and 8 and it will beapparent that a portion of the body of fluid is directly subjected tothe influence of both plates, Whereas the intensity of this doubleinfluence decreases and is almost nil in that portion of the body of thefluid located between adjacent ed es of the plates. From the above, itwill e apparent that the spacing of the blades of a propeller may besuch that their cooperation will set up conflicting streams of lines offlow which will prevent each blade from operating effectively on th'eliquid or fluid and that on the other hand the Spacing may be such thatthe blades will, in eil'ect, operate independently and consequently withno appreciable detrimental effect on each other. In other Words, theremay be a negative cooperation between the plates such that each platewill operate effectively in the production of a stream of liquid orfluid and will exert little or no detrimental effect on the operation ofthe other plate.

In Fig. 6, I have illustrated a plate 8 submerged within a body of fluidand moving in the direction of the arrow l0. It will be noted that thedirection of the motion of the plate is at an angle lesss than 90 to theface of the plate. Under such conditions, a movement of the plate fromthe position CD to the dotted line position EF will accomplish the sameeffect, so far as displacement in the direction of'the arrow llv isconcerned, as if a plate having the width- GD, and a length equal tothat of the plate 8a had been moved from the position indicated by thedotted line GD in the direction of the arrow 1l to a position CF. Inother words, the movement of a plate through a liquid or fluid in adirection at an angle less than a right angle to the plane of' the faceof the plate will occasion a displacement in any direction within thebody of fluid which will be proportional to the projected area of theplate on a plane at right angles to the direction of the displacementunder consideration. Such a displacement will also set up stream linesWithin the body of the fluid substantially similar to the stream linesdiagrammaticall illustrated in Figs. 4 and 5, and the velocity alongthese stream lines in the direction of the displacement underconsideration will increase with the convergence of the stream lines andwill reach a maximum velocity at the trailing edge of the moving plate.It will however, be apparent that the stream lilies so produced will beinfluenced both by the direction of motion of the plate and the positionof its effective face. In other words, the stream lines set up withinthe body of the fluid wiil be inclined with relation to both the arrows10 and 1l and the stream of fluid leaving the plate will, therefore, bedeflected an amount depending upon the motion of the plate and theangular position of the plate with relation to its direction of motion.This deflection of the stream lines occasions a reduction in the crosssectional area of the stream; and, as a result, the velocity of flowwithin the deflected stream is materially increased over that of thefluid moving toward the` plate, since the area times the flow must inboth cases be equal.

It will be apparent that the deflection of the fluid leaving the plate8'* must be occasioned without shock. This means that the direction ofthe lstream lines of the fluid `approaching the plate must conform tothe direction of the stream lines of the yfluid leaving the plate. Undersuch conditions, the change of direction will be gradual and the streamlines leaving the plate will, in effect, be a continuation of thoseapproaching the plate with the result that gradual change in directionwill be accomplished along curved stream lines both in the fluidapproaching and in the fluid leaving the plate. In addition, thesecurved stream linesl will converge both by reason of the vena contractaefi'ect illustrated in Figs. 3 and 4, and the change of direction offlow, illustrated in Fig. 6. In order to produce a gradual accelerationof the fluid, without subjecting it to shock,

1t is necessary that the relative motion of the fluidand the plateshould be such that the fluid approaches the Working face of the platealong lines which are substantially parallel to the surface of the plateat the entrance or leading edge. It will, however, be apparent that withsuch a condition of relative motion Vbetween the fluid and the plate,the plate would have no propelling effect on the fluid and consequentlyit is necessary to so arrange the surface of the plate that the angle ofthe surface with relation to the direction of motion of the plate willincrease from the leading to the rear or trailing edgeof the plate. Itis also necessary that this increasing pitch be so proportioned that thefluid will be gradually accelerated a sufficient amount to compensatefor the convergence of the stream lines occasioned by the vena contractaeffect and the change in direction of flow.

The fact that the vena contracta of a jet has an arca which is less thanthat of the orifice of its origin indicates that the velocity of flow atthe vena contracta is greater for the reason that for the flow of fluidsin a conduit, velocit times area is constant. However, Where t edisplacing element moves in a plane substantially atright angles to theaxis of the approaching column of fluid, as is illustrated in Fig. 6,the deflection of the stream occasions a still further convergence ofthe stream lines; and, consequently, the latter convergence occasions anincrease in the velocity of flow which is greater than that occasionedby the reduction in area at the vena contracta.

The propeller blades of my improved pump must, therefore, have anincreasing axial pitch, or such a ratio of pitch ratios of the trailingedges with respect tothe leading edges of the blades, so that in actingupon the fluid they will occasion a velocity of flow which is greaterthan that occasioned by the contraction of the stream as it traversesthe propeller and by the change of direction of flow of the fluiddischarged from the propeller. Also the ratio of projected blade area tothe annulus or disk area should be such as to secure an undivided andhomogeneous discharge so as to completely fill the rasing and avoidlosses due to eddying or shock. As the area ratio is inverselyproportional to the ratio of pitch ratios, the propeller blades arespaced apart suiiiciently so that no substantial loss is involved duc tostream line interference in the fluid approaching the blades.Experiments indicate that the angular deflection of Ydischarge may vary,for example, from 15 to 30P with respect to the axis of the approachingcolumn.

In Fig. 7, I have section o-f a propeller tion is taken alongillustrated a developed blade in which the seca cylindrical surfacemidway between the root and tip of the blade. I have also illustrateddiagrammatically the direction of the lines of flow occasioned by movingsuch a blade through a Huid or liquid in the direction of the arrowassociated with the figure. The blade l2, illustrated, increases inaxial pitch from the leading to the trailing edge in accordance with theempirical rule above set forth. In Fig. 8, I have shown a similarlydeveloped section of a pump propeller having two such blades and I havediagrammatically illustrated the lines of flow occasioned by `auch apropeller where the direction of rotation is indicated `by the arrow.Lines AA and BB associated with Fig. 8, indicate the common surface ofcleavage in developing the section.

In Fig. 8, I show a pump propeller which 1s provided with two or moreblades and it will be apparent that the projected area of the bladesshould be such as to avoid the effect of fiow interference at-the inletside. lVith respect to the number of blades which the propeller shouldhave, I have experimentally determined that the best elliciency isobtained with the fewest blades and that the eiiicienc'v decreases byabout 4.5% for each additional blade where the ratio of pitch ratios andthe ratio of projected to disk areas remain constant.

In accordance with my invention, the ratio of projected blade to diskareas varies with the contraction co-eiicient and the ratio of pitchratios of the trailing edges with respect to the leading edges of theblades varies inversely with the area ratio. For low discharge pressuresor heads, the value of the contraction co-eliicient is usually 'given as0.625; however, as has been experimentally determined, the contractionco-eflicient increases with the discharge pressure or head. Therefore,in desi ing my propeller pump, first of all, the discharge pressure orhead is takeninto consideration in correctly determining the rojectedarea ratio and the ratio of pitch ratios.

Assuming, by Way of example, that the contraction co-elficient is 0.625,for low discharge pressure or heads, it will be apparent that thevelocity of liow is in the ratio cient, the angularity or pitch of thedisplacing surface must be such that its trailing edge will, in actingupon the fluid, oc-` clasion a velocity of flow which is greater t anand in addition be such as to .occasion an increase in flow which isgreater than the combined acceleration required by the vena contracte.and by the change of direction. On the basis of a value of 0.625 for thevena contracte, the above theory indicates that theV pitch of thetrailing edge should at least be equal to or greater than 1.85 times thepitch of the leading edge. Experiments which I have conducted indicatethat the pitch of the trailing ed e should actually be about 2 to 2%times that of the pitch of the leading edge. This discrepancy isprobably accounted for by friction and edge losses which are ditlicultto estimate with theoretical accuracy. The increase in pitch justdescribed is in an axial direction with relation Vto the propeller,since the radial pitch of the blades is constant.`

Figs. 9, 10, and 11 are illustrative of certain experiments which I haveconducted. In these experiments, a lovi7 head or back pressure Wasinvolved and the generally accepted contraction co-etlicient of 0.625was used.

In Fig. 9 for a vena contracte. co-eflicient of 0.625, the curve showsthat the maximum eliciency was attained with blades having a projectedarea ratio of approximately 60%; however, it is to be understood thatthe projected area ratio may vary, such ratio being dependent upon therelative area required to secure an undivided and homogeneous dischar ewhich completely fills the pump casing or a ratio of pitch ratios of thetrailing edges with respect to the leading edges of the blades necessaryto accelerate the fluid traversing the propeller in order to compensatefor velocity increases occasioned by the contraction of the stream andby the discharge thereof at an angle.

Fig. l() indicates the variation 1n elliciency occasioned by employingpump propellers or having blades of different pitch ratios where theprojected area remains constant. The curve indicates that the maximumefficiency was attained when the pitch ratio of the outlet or trailingedge is two and one-half times that of the leading edge.

In Fig. 11, I show the effect on the'efliciency of the number of blades,assuming that the pitch and area ratios remain constant. It will benoted that the efficiency decreases with the increase in the number ofblades While apparently a maximum efficiency is obtained with aone-bladed propeller. Obviously, however, a one-bladed propeller wouldordinarily not be employed because of its inherent unbalance andconsequent tendency to vibration.

I desire it to be distinctly understood that the diagrams in Figs. 9,10, and 11 are merely illustrative in nature and were determinedexperimentally for aloW discharge pressure or head; and, accordingly, Ido not desire to be limited to the exact proportioning of partsindicated lthereby, as. there are many factors entering into the actionof propeller pumps and tending by their action and inter-action toslightly shift the salient points of these operating curves 1 n onedirection or the other. For example, if the contraction co-eliicient ischanged, the curves would be changed accordingly.

The requirement that the ratio of projected blade area to disk area,referred to also as the area ratio, shall be suflicient to secure anundivided and homogeneous discharge is obvious from a consideration ofFigs. 12, 14 and 15. Also, it will be apparent, from Fig. 12, that theratio of pitch ratios of the trailing with respect to the leading edgesof the blades varies inversely as the projected blade area to theannulus or disk area. In Fig. 12, I show diagrammatioally and indevelopment, two propeller blades 21 having a smaller ratio of pitchratios than the pair of blades 30. The blades 21 should have such aratio of projected to disk area that the fluid discharged therefrom isundivided and homogeneous. Accordingly, the parallel lines indicate thestream lines of flow from the blades 21 and it Will be seen that suchlines a-djoin and that the fiuid is not divided by the blades nor is theHuid discharged from one blade intercepted by the other. In like manner,the dash lines from the blades 30 indicate how these blades should bedesigned in order to secure an undivided and homogeneous discharge.

The importance of having the fluid discharged in an undivided andhomogeneous stream is obvious from a consideration of Fi s. 14 and 15.In Fig. 14, I show a conduit 31 connected to a larger conduit 32 so asto discharge fluid abruptly thereinto. Such a construction is veryinefficient as a velocity-pressure conversion device on account of thelosses due to eddies, as indicated in the view. Fig. 15 shows how theapparatus shown in Fig. 14 should be modified in order to produce anefficient velocitypressure conversion device wherein little, if any,eddy losses take place. If the streams of fluid discharged from thepropeller blades should not be contiguous so as to constitute anundivided and homogeneous stream, eddy losses would take place for thesame reason as in Fig. 14. A consideration of Figs. 14 and 15,therefore, shows the importance not only of having the streams of fluiddischarged by the propeller blades contiguous and parts of an undividedand homogeneous stream, but also the importance of having the pumpcasing entirely filled in avoid shock and eddy losses.

It is also characteristic of the blades of my propeller thatthe ratio ofpitch ratios varies inversely as the cosine of' the angle includedbetween the trailing edge and the plane of rotation. See Fig. 13. Inthis view, the blade 21, having the smaller ratio of pitch ratios,includes a smaller angle alpha between the trailing edge and the planeof rotation than the angle alpha included between the trailing edge ofthe blade 30 and the plane of rotation.

As hereinbefore pointed out, my invention comprises a propeller pump inWhic the ratio of projected blade area to annulus area varies with thecontraction co-efficient; and, of course the ratio of pitch v ratiosvaries inversely with the area ratio. I have discussed the generalcharacteristics of my improved pump, as Well 'as the pertinent theory inexplanation thereof. I have also considered in detail a pump in whichthe contraction co-efiicient was taken as 0.625. The situation in whicha larger co-elficient is involved, due to increased back pressure orhead, will now be considered. In a case of this kind, preliminarily tothe proper design of a pump made in accordance with my invention, it isnecessary, first of Iall, to determine the back pressure or head andthen to determine the ratio of projected blade to annulus or disk area,which varies with the inrease in the contraction coefiicient andtherefore with the increase in discharge pressure or head. After thearea ratio is determined, then in accordance with the rule that theratio of pitch ratios of the trailing edge with respect to the leadingedge v-aries inversely as the area ratio, the ratio of pitch ratios maybe ascertained. If the co-efiicient of contraction increases, this meansthat the propeller blades are called upon to accelerate `the fluid lessand less to compensate for increase in velocity due to contraction ofthe stream traversing the propeller.

The effect of increasing back pressures or head is illustrated bydiagrammatic Fig. 16. From this view, it will be seen that, for anincrease in pressure or head, the co-eicient of contraction, indicatedby the curved line designated co-efiicient of contraction, increases andthat the area ratio varies with the contraction co-eiicient, and thatthe order to hoo ratio of pitch ratios so designated) varies tractionco-etlicient.

The advantages in improved eficiency attained in the employment of thepump of this invention arise from the absence of eddying currents in thestream passing to, through and from the propeller, yand from (indicatedby the curve inversely with the conthe union Without shock of theseparate columns of fluid projected or delivered by the separate bladesot' the propeller to form a homogeneous stream outwardly flowing fromthe propeller. The essential relations in the propeller construction ofaxial pitch and projected area to the contractional coefiicient of thestream traversing the propeller, as hereinabove fully described and setfforth in the appended claims, result in the attainment of the aboveindicated improved operative characteristics of the propeller pump .ofthe present invention.

While I have shown my invention in but one form, it will be obvious tothose skilled in the art that it is not so limited, but is susceptibleof various other changes and modi cations without departing from thespirit thereo and I desire, therefore, that only such limitations sh-allbe placed thereupon as are imposed by the prior art or as arespecifically set forth in the appended claims.

What I claim is:

l. In combination in a propeller pump or fan, a propeller comprising ahub portion, blades mounted thereon and having a rojected area ofapproximately 60% the isk area, and an axial pitch at the outlet edge,so pro ortioned with relation to the pitch at the in et edge as tocompensate for the increase in velocity due tothe contraction of thestream lines in the fluid traversing the propeller and the contractiondue to the angularity of the stream lines leaving the blades.

2. In combination in a fluid impeller of the propeller type, a propellercomprising a hub portion, blades mounted thereon and having a projectedarea of approximately 60% the disk area, and an increasing axial pitch,the pitch ratio of the leading edge of cach blade being such as toreceive the fluid without shock and increasing to a pitch ratio at thetrailing edge such as to occasion an increase in velocity greater thanthat occasioned by the contraction of the stream lines as the fluidtraverses the propeller and the contraction occasioned by the angularityof the stream lines leaving the blades of the propeller.

3. In combination ina pump, a propeller. comprising a hub portion,blades mounted thereon. having a projected area materially less than thedisk area. and having an increasing axial pitch, the ratio of the pitchratios of the trailing to the leading edge having an inverserelationship to the ratio of the projected area to the annulus or diskarea.

4. In combination in a pump, a propeller, comprising a hub portion,blades mounted thereon, having a. projected area materially less thanthe disk area, and having an increasing axial pitch, the ratio of thepitch ratios from the trailing to the leading edge being greater thanthe ratio of the disk area to the projected area.

5. In combination in a comprising blades having increasing pitch fromthe leading to the trailing edge, the increase of pitch having adefinite relation to the projected area ratio.

6. In combination in a pump, a propeller comprising blades havingincreasing pitch from the inlet to the outlet edge, the increase inpitch being inversely proportional to the projected area ratio of theblades and also inversely proportional to the cosine of the angle whichthe trailing edge of the blade makes with the plane of rotation.

In combination in a propeller pump, a propeller having a projected areamaterially less than the disk area and an increasing pitch from theleading to the trailing edge, the ratio of the pitch ratios being suchas to compensate for the increase in velocity occasioned by thecontraction of the stream lines of the fluid traversing the propellerand the contraction of the stream lines occasioned by the angularity ofthe stream lines leaving the propeller.

8. In combination in a pump, a casing having Working passages formedtherein and a propeller mounted within said casing and aving a projectedarea materially less than the disk area and increasing axial pitch suchthat the separate streams projected by the separate blades of thepropeller unite to just fill the delivery passage of the pump withoutshock or cavltation.

9. In combination in a propeller pump, a, casing having working passagesformed therein, and a propeller located within the Working passages ofthe pump and having a projected area of approximately half the diskarea, and an increasing pitch such that the separate streams projectedby the separate blades of the propeller unite to just ll the deliverypassage of the pump without shock or cavitation.

10. In combination in a propeller pump, a casing having aconverging-diverging Working passage, and a propeller located at thethroat of said passage, and having a projected area of approximately 55%of the disk area of the propeller and an increasing pitch from theleading to the trailing edge of each propeller blade.

11. In combination in a propeller pump, a casing having aconvergingdiverging Working passage, and a two-blade propeller lopump, apropeller cated at the throat of said passage and having a projectedarea of approximately half of' the disk area of the propeller, andanincreasing pitch from the leading to the trailing edge of each blade.

1Q.. In combination in a propeller pump, a casing having aconverging-diverging flui passage, a tWo-bladed propeller located at thethroat of said passage and havin a projected area substantially lessthan t e disk area and an increasing axial pitch whereby the separatestreams of fluid projected by eachblade unite to form a single streamsubstantially filling the outlet portion of said passage and homogeneousthroughout as regards continuity of flow.

13. In combination in a propeller pump, a casing having aconverging-diverging flui passage, a two-bladed propeller, located atthe throat of said passage, and having a projected arca of substantiallyhalf the disk area.

14. In combination in a propeller pump, a casing having aconverging-diverging fluid passage, a tWo-bladed propeller, located atYthe throat of said passage, and having a projected area ofapproximately half the disk area, and having an increasing axial pitch.

15. In combination in a propeller pump, a casing, a ytvvo-bladedpropeller located within the casing and having a projected areamaterially less than the disk area, and an increasing axial pitch suchthat the axial pitch at the trailing edge of each blade is substantiallytwice that at the leading edge.

16. In combination in a propeller pump, a casing, a two-bladed propellermounted therein of constant-radial pitch and having a projected area ofapproximately one half the disk area and an increasing axial pitch.

17. In combination in a propeller pum ay casing having aconverging-diverging uid passage, a tWo-bladed propeller mounted thereinat the throat of said passage and of increasing axial pitch, the ratioof the pitch ratios from the leading to the trailing edge beingsubstantially inversely proportional to the ratio of the projected areato the disk area.

18. In combination in a propeller pump, a casing having aconverging-diverging fini passage, and a propeller mounted at the throatof said passage and having blades, the projected area of the bladesbeing materially less than the annulus or disk area, the radial pitch ofthe blades being constant, and the axial pitch of the blades increasingfrom the leading to theitrailing edges.

19. In combination in a propeller pump, a casing having aconverging-diver'ging fluid passage, and a propeller mounted at thethroat of said passage and having blades, said blades having a projmately one half the disk area, a constant ected areaapproxi-yradialpitch and an axial pitch increasing from the leading tothetrailing edges.

20. In combination in a propeller pump, a casing having aconverging-diverging fluid passage, a propeller located therein at thethroat of said passage and having a constant radial pitch and aprojected area materially less-than the disk areal 21. In combination ina propeller pump, a casing having a converging-diverging fluid passage,a two-bladed propeller located therein at the throat of said passage,having a constant radial and an increasing axial pitch, and a projectedarea of approximately half the disk area.

22. In combination in a propeller pump, a casing and a propellerarranged therein, the axial blade pitch of the propeller increasing fromthe leading tothe trailing edges, the ratio of the pitch at the trailingedge to the pitch at the leading edge being approximately an inversefunction of the pressure head at the discharge side of the propeller.

23. In a propeller pump, a propeller having blades which increase inaxial pitch from the leading to the trailing edges, the ratio y"of thepitch at the trailing edge of the blade to the pitch at` the leadingedge thereof being approximately an inverse function of the contractionco-eiiicient of the stream traversing the propeller.

24. In a propeller pump, a propeller having blades which increase inaxial pitch from the leading to the trailing edges, the rate of increasein the blade pitch being approximately an inverse function of thepressure head at the discharge side of the propeller.

25. In a propeller pump, a propeller having blades which increase inaxial pitch from the leading to the trailing edges, the rate of increasein the pitch of the blade being approximately an inverse function of thecontraction (3o-efficient of the stream traversing the propeller.

26. In a propeller pump, a propeller having blades whose ratio ofprojected blade area to annulus or disc area is proportional to afunction of the contraction of the stream traversing the propeller andWhose ratio of pitch ratios of the trailing edges of the blades withrespect to the leading edges is approximately proportional to an inversefunction of the area ratio.

27. Ina propeller pump, a propeller having blades Whose ratio ofprojected blade area to annulus or disc area is proportional to theextent of contraction of the stream traversing the propeller and whoseratio of pitch ratiosof the trailing with respect to the leading edgesis approximately inversely proportional to the area ratio.

28. In a fluid impelling device, a plurality of similar blades mountedfor movement in the samexpath, the projected area of said between 50%and 62.5% of the area of said blades on the surface swept over by thesurface, said blades having an increasing discharge edges of said bladesbeing bepitch from the leading to the trailing edges tween 50% and 62.5%of the area of said thereof, the ratio of the pitch ratios of thesurface. leading to the trailing edge having a con- 29. In a fluidimpelling device, a plu` verse relationship to said area ratio. ralityof similar blades mounted for move- In testimony whereof, I have,hereunto ment in the same path, the projected area subscribed my namethis 23rd day of May, of said blades on the surfacelswept over 1924. 1by the discharge edges of said blades being HENRY F.,SCHMIDT.

the samehpath, the projected area of said blades on the surface sweptover by the discharge edges of said blades being between 50% and 62.5%of the area of said surface.

29. In a fluid impelling device, rality of similar blades mounted formovement in the same path, the projected area of said blades on thesurface swept over by the discharge edges of said blades being a plu-Gerticate of Correction.

in Letters Patent No. 1,596,459, of Lansdowne, Propeller Pums, an errorappears in the It hereby certified that 1926, to Henry F. Schmidt,

tion as follows:

edges of the blades; and that the said Letters Patent HENRY F. SCHMIDT.

granted August 1 7, Pennsylvania, for an improvement 111 printedspecification requirinor correcage 8, line 124, claim 27 after the wordtrailing insert the words should be read with this correction thereinthat the same may conform to the record of the case in the Patent Oice.

Signed and sealed this 2d day of November, A. D. 1926.

[smal WM. A. KINNAN, 4 Acting Commissioner of Patents.

Certificate of Correction.

It is hereby certified that in Letters Patent No. 1,596,459, grantedAugust 17, 1926, to Henry F. Schmidt, of Lnsdowne, Pennsylvania, for animprovement in Propeller Pumps, an error appears in the printedspecification requirinff correction as follows: Page 8, line 124, claim27. after the word trailing insert the Words edges of the blades; andthat the said Letters Patent should be read with this correction thereinthat the same may conform to the record of the case in the Patent Signedand sealed this 2d day of November, A. D. 1926.

[SEAL] WM. A. KINNAN,

` Acting Commissioner of Patents.

